You can't do this and get DVD quality, but you can do it on a computer by playing through an analog-to-digital capture device (some computer graphics cards included this), or sometimes it works to hook up a VHS player to a DVD recorder.
If you are asking about converting copy-protected commercial VHS tapes, you might need to run the composite video signal through a time-base corrector, for early VHS recordings. After 1984, when the industry started using Macrovision (more than one technology) the copy protection is harder to defeat than the earlier practice of messing with the time-base. For the Macrovision technique of inserting pulses into the VBS, there were filtering devices sold in the VHS era to remove the pulses that told a recorder "don't record this." The technique of messing with the colorburst is harder to fix.
The cost of the equipment to do what you want to do will likely exceed the cost of replacing your favorite titles with DVD versions, particularly since there is now a huge market in used DVDs. I've built my DVD library with titles I've bought used at $1 to $5.